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Trying to Understand the Why on Load Data

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Chief TC

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Joined
Mar 9, 2023
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Oregon
So I am working on developing a new load for my M1917 because I got a good deal on 500 of 180gr SMK factory seconds. These perform much differently than the Hornady 178 match bullets I currently use. My question is what are the factors behind the vast differences between these 2 bullets. I noticed the max charge on AA4350 was 55.9gr for the Hornady 178gr match bullet and 60.3gr max for the 180gr SIE SBT. Since the weight is almost exactly the same, then is it the angle of the ogive that dictates how much pressure the bullet can handle? Thanks.
 
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Chief TC said:
So I am working on developing a new load for my M1917 because I got a good deal on 500 of 180gr SMK factory seconds. These perform much differently than the Hornady 178 match bullets I currently use. My question is what are the factors behind the vast differences between these 2 bullets. I noticed the max charge on AA4350 was 55.9gr for the Hornady 178gr match bullet and 60.3gr max for the 180gr SIE SBT. Since the weight is almost exactly the same, then is it the angle of the ogive that dictates how much pressure the bullet can handle? Thanks.
Click to expand...
It’s not correct to assume any publisher or lab tests to the breaking point. The phrase, “…how much pressure the bullet can handle,” is not appropriate.

Labs test by a variety of criteria and the first thing you should compare are the methods and criteria used by the publisher of the lab’s results.
 
GeoDudeFlorida said:
It’s not correct to assume any publisher or lab tests to the breaking point. The phrase, “…how much pressure the bullet can handle,” is not appropriate.

Labs test by a variety of criteria and the first thing you should compare are the methods and criteria used by the publisher of the lab’s results.
Click to expand...
I can understand that but what I am wondering is why can the SIE SPBT handle more pressure than the Hornady match. Bullseye says it is a variety of factors.
 
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The only comparisons I find even close to even are done in the same lab. If comparing diffrent manuals every variable is in play including powder lot numbers. Testing in your gun is the be all end all, and one trip to the range to test for pressure will give you the only facts that matter.... one thing to note is how long you let a test round cook in your barrel and how many were shot previously. You shoot 3 fouling and 10 in a row your barrel will be hot, and if the 11th test round is the same as the tenth but sits for a while it can show pressure where the one previous did not. That's the long way to say have cooling periods during pressure tests commensurate with the barrel weight.
 
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Chief TC said:
I can understand that but I am what I wondering is why can the SIE SPBT hand more pressure than the Hornady match. Bullseye says it is a variety of factors.
Click to expand...
There is no relationship between the loading tests and the amount of pressure the bullet can “handle.”
This is from IMR, ca. 2003, which the company states is provided free of charge to the public. Please read it carefully.
IMG_2344.jpeg
Emphasis is original to the text.
 
I think maybe I am incorrectly talking about pressure. With the same AA4350 powder, the SIE SBT bullet with max loads is around 58,000 PSI while the Hornady ELD match is around 51,000. So I understand these are not the maxes each bullet can handle but it seems one bullet has a higher tolerance than the other??? Not sure if I am asking the right question. Trying to learn.
 
Chief TC said:
I think maybe I am incorrectly talking about pressure. With the same AA4350 powder, the SIE SBT bullet with max loads is around 58,000 PSI while the Hornady ELD match is around 51,000. So I understand these are not the maxes each bullet can handle but it seems one bullet has a higher tolerance than the other??? Not sure if I am asking the right question. Trying to learn.
Click to expand...
I look for bullets significantly below operational expected pressure to see if the powder is compressed or if there is a big difference in bullet length reducing case capasity.
 
Walkalong said:
That's not a huge difference, and sometimes they stop because more wasn't as stable/consistent in pressure,
not because they are running up against the max pressure allowed.
Click to expand...
Thanks - this really helped make the connection. I was thinking more about rating and max capacity rather than a bullet being pushed at max chamber pressure.
 
Walkalong said:
That's not a huge difference, and sometimes they stop because more wasn't as stable/consistent in pressure,
not because they are running up against the max pressure allowed.
Click to expand...
That instability is discussed in the Lyman 45th in how loads are selected for their manual. I have seen these data anomalies in pistol so in theory would apply equally in rifle but I've not encountered them...
 
Chief TC said:
I think maybe I am incorrectly talking about pressure. With the same AA4350 powder, the SIE SBT bullet with max loads is around 58,000 PSI while the Hornady ELD match is around 51,000. So I understand these are not the maxes each bullet can handle but it seems one bullet has a higher tolerance than the other??? Not sure if I am asking the right question. Trying to learn.
Click to expand...
Another way to think about it: The tests with the Sierra indicate it peaks SAAMI max pressure at around 58Kpsi with x-grains of powder so that’s where the testing stops. The lab testing the Hornady found a wide stability sweet spot in the 51Kpsi zone so that’s where the testing stopped.

I’m not certain this is exactly how the tests were conducted but it makes more sense than testing to the point of imminent failure. Did you see the part in the quoted text about the tests being conducted on a universal receiver and commercial barrels? That’s an important thing to keep in mind; testing is not performed with off the shelf firearms but with lab equipment. All the lab is testing is velocity and pressure. They are not testing accuracy - or maybe they just don’t publish the accuracy results for liability purposes.
 
Nosler produces the most accuracy data and Lyman lists the best powder for the loading they found. If you find irregularities look for more data. 30-06 is listed and tested by everyone. I plot all the loads and look for the overlap to test in. You may find with 5 sources 1 is annomolus and doesn't fit with the rest. More information/data never led to worse decisions in my reloading room.
 
Walkalong said:
That's not a huge difference, and sometimes they stop because more wasn't as stable/consistent in pressure,
not because they are running up against the max pressure allowed.
Click to expand...

And sometimes they hit a point where more powder doesn’t give more speed and just increases pressure. It’s a point of no more returns kinda thing.
 
Preasure listed is as close as they could get without exceeding top preasure. The higher the preasure listed the more consistent the load. I'm rooting around different books to find that statement. Think it was before the hodgdon magazines. Similar to the 296 and H110 story. So, if max is 60,000psi and your shots average 58,000 but don't go over 60,000 your in. If you average 58,000 and go over with 1 2 or 3 rounds it's a do over. If you get down to 50,000 and none go over psi your in.
 
Show Me said:
Preasure listed is as close as they could get without exceeding top preasure. The higher the preasure listed the more consistent the load. I'm rooting around different books to find that statement. Think it was before the hodgdon magazines. Similar to the 296 and H110 story. So, if max is 60,000psi and your shots average 58,000 but don't go over 60,000 your in. If you average 58,000 and go over with 1 2 or 3 rounds it's a do over. If you get down to 50,000 and none go over psi your in.
Click to expand...
That's round about what Lyman says also... helped me "get it"
 
Chief TC said:
So I am working on developing a new load for my M1917 because I got a good deal on 500 of 180gr SMK factory seconds. These perform much differently than the Hornady 178 match bullets I currently use. My question is what are the factors behind the vast differences between these 2 bullets. I noticed the max charge on AA4350 was 55.9gr for the Hornady 178gr match bullet and 60.3gr max for the 180gr SIE SBT. Since the weight is almost exactly the same, then is it the angle of the ogive that dictates how much pressure the bullet can handle? Thanks.
Click to expand...
If I may inquire as to which manufacturer of the 1917. To attempt to compare say Winchester to a Remington or Eddystone. With said bullets. Because I am starting the same venture with I believe the same bullets. Soon as I can get my front sight drifted a little to the right. A few rounds in it, Hornady whitetails 5 shots, same hole. As did the Winchester service grade ammo. The few 168gr match I loaded, a little lower but almost the same to the right 5 in one hole. The 178gr I have not shot yet. My Winchester retains the original barrel from Armory I believe, the 5 left. Stamped 1918, June I think. I will be trying to follow your posts
 
Nipty said:
If I may inquire as to which manufacturer of the 1917. To attempt to compare say Winchester to a Remington or Eddystone. With said bullets. Because I am starting the same venture with I believe the same bullets. Soon as I can get my front sight drifted a little to the right. A few rounds in it, Hornady whitetails 5 shots, same hole. As did the Winchester service grade ammo. The few 168gr match I loaded, a little lower but almost the same to the right 5 in one hole. The 178gr I have not shot yet. My Winchester retains the original barrel from Armory I believe, the 5 left. Stamped 1918, June I think. I will be trying to follow your posts
Click to expand...
I have a 1917 Eddystone. Seems as long as the bullets weights are the same, it will put virtually any good production ammo in the same 1" circle @ 100 yards. Been that way since the day I got it back in 1970. Barrel has been shortened, recrowned and original sights replaced with Williams. Was my primary deer rifle for 35 years until I quit hunting deer with a long gun completely and went with revolvers. Was like carrying a tree trunk around in the woods, but it never missed.
 
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